How a Triple Crown Contender Threatens to Edge the Bluegrass State Out of the Picture

California is hardly known as an epicenter of thoroughbred breeding. But on Saturday, the Belmont Stakes will include the first California-bred Triple Crown contender, leaving the actual industry leader, Kentucky, to pour another bourbon and dream of next year.

Kentucky produces about one-third of all the registered thoroughbred foals in the U.S. according to the Jockey Club, the breed's registry. California accounts for about 8% of...